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JavaScript - Getelementsbytagname
Hello CodingForums.
I have a script to increase the fontsize on my website.. It works perfectly, but currently it's only targetting my <p> tag and I want it to target my h2 and h3 aswell.. How can I do this? Code: var min=8;
var max=18;
function increaseFontSize() {
var p = document.getElementsByTagName('p');
for(i=0;i<p.length;i++) {
if(p[i].style.fontSize) {
var s = parseInt(p[i].style.fontSize.replace("px",""));
} else {
var s = 12;
}
if(s!=max) {
s += 1;
}
p[i].style.fontSize = s+"px"
}
}
function decreaseFontSize() {
var p = document.getElementsByTagName('p');
for(i=0;i<p.length;i++) {
if(p[i].style.fontSize) {
var s = parseInt(p[i].style.fontSize.replace("px",""));
} else {
var s = 12;
}
if(s!=min) {
s -= 1;
}
p[i].style.fontSize = s+"px"
}
}
Similar Tutorialstoday looking through my logs (errors) and one that came up was Code: element.getElementsByTagName is not a function from the source Code:
getByAttribute = function(element, strTagName, strAttributeName, strAttributeValue)
{
var arrElements = (strTagName == "*" && element.all)? element.all : element.getElementsByTagName(strTagName);
Can anyone help me out here? thanks Hello, I am just starting out learning JavaScript and I have just reach the DOM section of my course. I have a page with 10 <a> tags on it and I have created the following JavaScript to tell me how many I have. Code: <script type="text/javascript">
var myLinks = document.getElementsByTagName("a");
console.log("We have ", myLinks.length ," many links on the page");
</script>
However in the console it reports this: We have 0 many links on the page This is not true as there are 10 links, 9 in the navgation section of the website and 1 in the footer. If someone can tell me what I am doing wrong that would be great. Thanks This is a question about a code for a javascript slide show which i think is very important to understand because slide shows are heavily used! This is the html: Quote: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <script language="javascript" script type="text/javascript" src="slideshow.js"></script> <title>Slideshow exercise</title> </head> <body> <h1> Slideshow exercicse</h1> <img class="slide" src="cityscape.jpg" width="400" height="300"> <img class="slide" src="Creative_design_sailing_leaves_under_blue_sky.jpg" width="400" height="300"> <img class="slide" src="Curiousity.jpg" width="400" height="300"> <img class="slide" src="raindrops-blue-garden-seamless-tile.jpg" width="400" height="300"> <p> Clic on image to view next slide</p> <p> Clic on image to view next slide</p> </body> </html> This is the .js file and my questions: Quote: var numslides=0;currentslide=0; var slides= new Array(); function MakeSlideShow(){ //find all images with the class "slide" imgs= document.getElementsByTagName("img");---------> question 1 for (i=0; i<imgs.length ; i++) { if(imgs[i].className != "slide") continue; slides[numslides]=imgs[i];----------------------------------->question2 //hide all but first image if(numslides==0) {imgs[i].style.display="block";} else{imgs[i].style.display="none";} imgs[i].onclick=NextSlide; numslides++;}//end of loop--------------------------->question3 } //end MakeSlideShow() function NextSlide(){ slides[currentslide].style.display="none";------------------>question4 currentslide++ if(currentslide >= numslides) currentslide=0; slides[currentslide].style.display="block";--------------->question5 } window.onload= MakeSlideShow; question1: does "imgs" automatically become an array here? If so, how can i print out its lenght? This is what i tried and it doesn't work-> var lengthimgs= imgs.length document.write(lengthimgs) question2: What is happening here? Is the imgs[i] array transferring its data into the slides[numslides] array? question3: If slides[numslides] and imgs[i] are interchangeable why can't this line be i++ instead of numslides++ question4: What is happenning to the slides array here? Is currentslide becoming a copy of numslides? question5: What does this do? Where does this line sent the code? Why this? Why hasn't "imgs[i].style.display="block";" already done the job for the display? Thanks i have this part of code in JS: Code: var receiveReq = getXmlHttpRequestObject();
function getXmlHttpRequestObject()
{
if (window.XMLHttpRequest)
{
return new XMLHttpRequest();
}
}
function getChatText()
{
if (receiveReq.readyState == 4 || receiveReq.readyState == 0)
{
receiveReq.open("GET","getChat_xml.php?chat=1&last=7", true);
receiveReq.onreadystatechange = handleReceiveChat;
receiveReq.send();
}
}
function handleReceiveChat()
{
if (receiveReq.readyState == 4)
{
var chat_div = document.getElementById('div_chat');
var xmldoc = receiveReq.responseXML;
var message_nodes = xmldoc.getElementsByTagName("message");
}
}
then in my getChat_xml.php i have: Code: $xml = '<?//xml version="1.0" ?><root>';
$last = 7;
$sql = "SELECT message_id, user_name, message, date_format(post_time, '%h:%i') as post_time" .
" FROM message WHERE chat_id = " . db_input($_GET['chat']) . " AND message_id = " . $last;
$message_query = db_query($sql);
while($message_array = db_fetch_array($message_query))
{
$xml .= '<message id="' . $message_array['message_id'] . '">';
$xml .= '<user>' . htmlspecialchars($message_array['user_name']) . '</user>';
$xml .= '<text>' . htmlspecialchars($message_array['message']) . '</text>';
$xml .= '<time>' . $message_array['post_time'] . '</time>';
$xml .= '</message>';
}
$xml .= '</root>';
echo $xml;
i get a "cannot cal a method getElementsByTagName of null" ??? i have no idea whats going on, help please? thanks (just started JS 2 weeks ago) -- this is also my first time posting here, if my post isnt following the proper template let me know and Ill fix it .. Thanks so much for taking the time to check this out in advance Im trying to make the first ul tag in the each slideMenus[] array index values have a position of left = 0px I keep recieving this error however ____________________________________________________ Error: slideMenus[i].getElementsByTagName("ul").style is undefined Line: 63 ------------------------------------------------------------------ the script in question is in [code]. Could someone tell me if I am just making a syntax error if not ill try redoing the whole thing. window.onload = makeMenus var currentSlide = null var timeID = null leftPos = 0 function makeMenus(){ var slideMenus = new Array() var allElems = document.getElementsByTagName("*") var slideListArr = new Array() for(var i=0 ; i < allElems.length ; i++){ if(allElems[i].className = "slideMenu") slideMenus.push(allElems[i]) } for(var i=0 ; i < slideMenus.length ; i++){ slideMenus[i].onclick = showSlide; Code: slideMenus[i].getElementsByTagName("ul")[0].style.left = "0px";
} document.getElementById("head").onClick = closeSlide document.getElementById("main").onClick = closeSlide } function showSlide(){ var slideList = this.getElementsByTagName("ul")[0] // mess with this if((currentSlide != null) && (currentSlide.id == slideList.id)) {closeSlide()} else{ closeSlide(); var currentSlide = slideList; currentSlide.style.display = "block"; timeID = setInterval('moveSlide()', 1); } } function closeSlide(){ if(currentSlide){ clearInterval(timeID); currentSlide.style.left = "0px" currentSlide.style.display = "none"; var currentSlide = null } } function moveSlide(){ var leftPos = leftPos + 5; if(leftPos <= 220) {currentSlide.style.left = leftPos + "px"} else{ clearInterval(timeID); var leftPos = 0} } Can someone please tell why this is not working in the browser. Here's my code: <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>Untitled Document</title> <script type="text/javascript"> var secondaryHeadings = document.getElementsByTagName("h2") alert(secondaryHeadings[0].innerHTML); </script> </head> <body> <div> <h1> Main Headline </h1> <h2> Sub-Headline</h2> </div> </body> </html> |
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